Conventionally, thermosetting-type (anionically curable type) epoxy resins are commonly used as adhesives. In order to meet with various applications, cationically photocurable epoxy resin compositions which can be cured by cationic polymerization of an epoxy resin induced by photo irradiation has been developed. This type of resin composition is adavantegeous in that it provides cured products having physical properties comparable with those from a thermosetting composition, it can be less inhibited by oxygen than a radical UV curable composition, and it exhibits a smaller shrinkage than a radical UV curable composition. It has been, therefore, used in various well-known applications such as a liquid crystal display, lamination in a digital video disk, and sealing of a device package.
For example, for the formation of a device with hollow packages, such as CMOS, a device is placed in a plastic or ceramic packages, then the upper part is sealed with a glass plate by UV curable type adhesives. With regard to the properties required, these adhesives have to have, in addition to the sealing and adhesive property with glass, excellent moisture resistance, water resistance, and storage stability both in high temperature and low temperature from the point of heat cycle and heat shock which a semiconductor device receives in a reflow furnace and the like and reliability over a long period.
In JP Laid-open No. 2003-327785 (Patent Document 1), we have disclosed a resin composition comprising an epoxy resin component comprising an alicyclic epoxy resin and an aromatic-ring containing epoxy resin, a cationic photoinitiator component and a filler selected from the group consisting of oxides, hydroxides and carbonates containing a Group II element in the periodic table. However, adhesives having more suitable properties for package application are demanded.
Also known in the art is thermally curable epoxy resin compositions which can be cured by cationic polymerization by the application of heat. For example, claim 1 of JP Laid-open No. 2003-238770 discloses “a epoxy resin composition for manufacture of inkjet head, which contains an alicyclic epoxy resin and/or bisphenol type epoxy resin as an epoxy resin, a photo-cationic polymerization initiator and/or thermo-cationic polymerization initiator as a curing agent, and at least an organosilicon compound as an additive wherein the organosilicon compound is the one which produces a silanol group upon light irradiation and/or heating and/or hydrolysis”. However, no specific example is disclosed in which both of photo-cationic polymerization initiator and thermo-cationic polymerization initiator are used. In addition, this document is directed to the composition for the specific application use where the durability to ink is enhanced by the use of a specific organosilicon compounds.
List of Documents
Patent Document 1: JP Laid-open No.2003-327785
Patent Document 2: JP Laid-open No.2003-238770